Device and method for calibrating a multiple-roller flattener

ABSTRACT

A metal measurement plate ( 5 ), having a size suitable for being placed between the set of upper rolls and the set of lower rolls of the leveler, has positioning means ( 60, 61, 62 ) for positioning it with respect to the rolls in the leveling direction, and strain gauges ( 51 ) for measuring elastic deformations of the plate during clamping on the leveler, said strain gauges being fastened to the plate so as to form several transverse rows of gauges ( 51  to  56 ) each located vertically in line with one of said rolls, on the opposite face of the plate with respect to said roll.

[0001] The present invention relates to a device and to a method forcalibrating a multi-roll leveler.

[0002] Multi-roll levelers are used as finishing tools for levelingsteel sheet. The general principle of leveling by multi-roll levelers,in particular of tension leveling, consists in making the sheet or stripto be leveled pass between two series of parallel rolls arranged so asto be mutually imbricated, the imbrication decreasing in the directionin which the sheet runs. As it passes between the rolls, it is deformedin bending alternately in one direction and then the other. Theamplitude of bending decreases from the entrance of the leveler to theexit, so that the steel strip is subjected to a succession ofalternating stresses suitable for eliminating or at least greatlyreducing the internal stresses that cause flatness defects. Theprogressive reduction in the deformation amplitude makes it possible toobtain, at the exit from the leveler, a strip as flat as possible andwith as few internal stresses as possible. In tension levelers, thestrip is driven through the leveler between a pay-out reel and a take-upreel by “S-shaped” drive units which make the strip run and also tensionit.

[0003] The ever tighter tolerances, in terms of flatness and internalstresses, imposed by strip or sheet users mean searching for the bestpossible way of controlling the operation of levelers, withpreadjustments being carried out, and the best possible understanding ofthe mechanical characteristics of the machine: play, clearances, spring,adjustment parameters, etc.

[0004] To gain a better understanding of the problems involved inachieving the desired improvement in the control of the behavior oflevelers, the reader will be reminded of the principal components of amulti-roll leveler in relation to FIGS. 1 to 5.

[0005] The drawing in FIG. 1 shows schematically such a leveler, whichcomprises a set of lower rolls 11 and a set of upper rolls 12, supportedby a lower beam 13 and an upper beam 14 respectively. The metal strip 10runs through the leveler between two motor-driven units 31, 32 of driveand tensioning drums arranged in an “S-shaped” configuration in thedirection of the arrow F. The rolls are all parallel and offset betweenthe top and the bottom, in the running direction of the strip, so thatthey can be mutually imbricated to a greater or lesser extent. As may beclearly seen, in the entry zone of the leveler, the strip is relativelyhighly deformed by undergoing alternating bending between the entryrolls 11 a, 12 a, 11 b, etc., which are highly imbricated, whereas inthe exit zone the deformations are very slight because the exit rolls 11m, 12 m, 11 n are only slightly imbricated or not at all.

[0006] The drawing in FIG. 2 also shows schematically an example ofmeans for adjusting the leveler, in order to adjust the imbrication ofthe rolls. The upper beam 14 is held on an upper frame 15 by adjustmentsassemblies 16 a, 16 b, 16 c, 16 d, for example of the type consisting ofa screw-nut with angle gear, two assemblies 16 a, 16 b being placed nearthe entry of the leveler and the other two 16 c, 16 d being placed nearthe exit respectively, and on each side in the longitudinal direction.The two entry adjustment assemblies 16 a, 16 b are connected by a driveshaft 17 a and a coupling 18 a and are driven together by an entry motor19 a. Likewise, the two exit adjustment assemblies 16 c, 16 d areconnected by a drive shaft 17 b and a coupling 18 b and are driventogether by an exit motor 19 b.

[0007] The couplings 18 a, 18 b are used to temporarily uncouple theadjustment assemblies that they connect, in order to be able to adjustthe transverse parallelism, or “dislocation”, between the lower andupper rolls, and to do so both at the entry and the exit of the leveler.Next, the imbrications of the rolls of the leveler are adjusted by meansof motors which drive, simultaneously and in an identical manner, theadjustment assemblies, either at the entry of the leveler or at theexit.

[0008] The parallelism or dislocation adjustment is carried out only inthe case of major interventions on the leveler. Calibration of theleveler is carried out more frequently, in order to readjust theimbrications of the rolls or to modify them according to thecharacteristics of the strips to be leveled.

[0009]FIG. 3 shows, also schematically, the leveler, seen from thefront, in order to show the means for adjusting the bending or the crownof the rolls. This is because, during leveling, the bending forcesexerted on the strip result, in reaction, in deforming the levelingrolls. To compensate for such deformation and prevent it in return fromcausing geometrical defects in the strip, the leveling rolls are in factsupported by back-up rolls that are themselves supported by press rolls.This assembly is mounted in a frame called a cassette placed on a set oftapered wedges or of actuators or else against supports that areindependent and height adjustable, these being distributed over thewidth of the leveler. In the example shown in FIG. 3, there are elevenrows of press rolls 21 placed over the width of the leveler. Thevertical position of the press rolls may be adjusted by means ofadjustable tapered wedges 22, each acting under all the press rollslocated on the same line parallel to the running direction of the stripand over the entire length of the leveler. The shape of the levelingrolls therefore depends on the vertical position of the press rolls.

[0010] An example of an adjustable press-roll system is shown in FIG. 5.In this example, the height of the press rolls is adjustable by means oftapered wedges 23 which are interposed between the support rolls and arigid lower frame 15′ and which slide one over the other. The relativedisplacement of the tapered wedges is effected by a cylinder 24, and maybe measured, for example, by a position sensor 25.

[0011] In the case of FIG. 3 for example, such systems have three pressrolls 22 a, 22 b, 22 c and 22 i, 22 j, 22 k located on each side nearthe ends of the rolls, where the deformations are greatest. In thecentral part, it is unnecessary to use such adjustable press rolls. Asmay be seen in FIG. 4 in a highly exaggerated manner, the press rollsmake it possible, by exerting under the rolls a vertical force ofgreater or lesser magnitude, to deform the latter, when empty and alsounder load, so that, during leveling, their profile is suitable forcorrecting the defects observed on the strip to be leveled.

[0012] To effect the overall adjustment of a leveler, there istherefore:

[0013] adjustment of the parallelism, or dislocation, of the levelerthat is to say substantially the adjustment of the parallelism betweenthe lower rolls and the upper rolls, this adjustment being carried outby acting on the screws for adjusting the position of the upper beam,taken independently between the adjustment screws on the right side andon the left side, after separating the couplings 18 a, 18 b;

[0014] adjustment of the imbrication of the rolls, at the entry and atthe exit of the leveler, the amount of imbrication being as a generalrule monitored by measuring the angle of rotation of the screws foradjusting the position of the upper beam, or by displacement sensorsbetween the beams at the leveler entry and exit;

[0015] adjustment of the crown of the rolls by means of actuators, asdescribed above, the value for each press roll being determined by themeasurement made by the sensors 25;

[0016] tension in the strip, generated by the “S-shaped” tensioningunits, the value of the tension being measured by a tensometer or fromthe electrical parameters of the reel motors; and

[0017] elongation generated during leveling and measured by a speeddifferential between entry tensioner and exit tensioner.

[0018] Moreover, the precise geometry of the pass path of the strip, onwhich the quality of the leveling depends, itself depends on the forcesgenerated during the pass and on the deformations of the strip, whichforces and deformations cause deformations of the machine, called spring(or deflection or camber, cedage in French).

[0019] To be able to exert effective control of the leveling, it isnecessary to know as precisely as possible the actual position of theleveling rolls and their geometry permanently during operation. It istherefore necessary to be able to determine what the geometry and theposition of the rolls are according to all the other parameters that canhave an influence on the rolls, that is to say the settings given to thevarious actuators and also the forces generated, that are likely tomodify the geometry and the actual position of the rolls.

[0020] To be able, with full knowledge of the situation, to adjust theleveler according to the characteristics of the strip to be leveled andto be able to set the actuators, especially the motors for adjusting theimbrications, it is therefore necessary to calibrate or set the leveler,that is to say to determine the base adjustments of the leveler that aresuitable for obtaining the desired leveling.

[0021] It is also highly desirable to be able to establish arelationship between the adjustment values that are controlled by theavailable actuators and the geometrical modifications of the levelingpath during operation, in other words to know the spring of the levelerand to take this into account in the adjustment of the imbricationmotors, in order as it were to compensate in advance for the spring thatwill be experienced during actual working.

[0022] Currently, the calibration of multi-roll levelers isconventionally carried out under no load using ground steel spacers, orunder load using metal spacers and lead bars, that are slid between thebeams of the leveler, then the beams are closed up in a parallel fashionuntil a precise gap is obtained between the two sets of lower and upperrolls, said gap being defined by a ground steel spacer, for example 8 mmin thickness, placed between the two sets of rolls. The leveler is thusplaced under loading conditions suitable for compensating for theinevitable mechanical play and in a stress state defined by thecompression of the lead spacers. The position of the leveler tighteningscrews in this state is then noted, said position then being taken asreference, with respect to which the subsequent working position isadjusted by bringing said adjustment screws into the positioncorresponding to the desired working position of the rolls and beingbased on the relationship linking the displacement of said screws to thecorresponding displacement of the rolls. It is also possible to adjustthe parallelism using this method, or to compensate for the dislocation,and even possibly to act on the press rolls in order to adapt thebending or the crown of the rolls, but only in an approximate manner.

[0023] During the abovementioned calibration procedure, the actual forceundergone by the beams, due to the compression of the lead spacers,remains unknown and is therefore not reliably representative of theforces encountered during actual working.

[0024] In particular, the known method has the consequence, observedexperimentally, of causing overtightening during the leveling of thinstrip.

[0025] As a result, the residual curvatures—bow and crown—are notcontrolled satisfactorily.

[0026] The object of the present invention is to solve theabovementioned problems. In particular, it is an object of the inventionto allow the characteristics of a multi-roll leveler to be determinedmore accurately, by carrying out a calibration under load, which isreproducible and under known forces. It is also an object of theinvention to determine the overall spring of the leveler, under variousloads, so as to be able to incorporate these values into adjustmentmodels. It is also an object of the invention to determine the influenceof the press-roll adjustments more accurately so as to be able to refinethe adjustments of the latter and be able to correct the transversespring of the leveling rolls, in order finally to obtain better flatnessof the leveled strip.

[0027] It is also an object of the invention to correct the dislocationof the leveler and its “tilt”. It is also an object of the invention tomake it possible to study the ability of a multi-roll leveler to provideprecise and reproducible adjustments corresponding to standard levelingloading cases.

[0028] With these objectives in mind, the subject of the invention is adevice for calibrating a multi-roll leveler in order to level a metalstrip, comprising a set of lower rolls and a set of upper rolls,arranged approximately in a parallel manner, perpendicular to theleveling direction in which the strip to be leveled runs.

[0029] According to the invention, the device is characterized in thatit includes a measurement plate made of metal, especially one with ahigh yield strength, and having a size suitable for being placed betweenthe set of upper rolls and the set of lower rolls, extendingapproximately over the entire length of said rolls, said plate havingpositioning means for positioning it with respect to the rolls in theleveling direction, and strain gauges for measuring the elasticdeformations of the plate, said strain gauges being fastened to theplate so as to form several transverse rows of gauges each locatedvertically in line with one of said rolls, on the opposite face of theplate with respect to said roll.

[0030] The subject of the invention is also a method for calibrating amulti-roll leveler, using the device of the invention, characterized inthat the measurement plate is placed in the leveler, positioned by thepositioning means so that each row of gauges is located vertically inline with a roll, and the two sets of rolls are brought closer togetherso as to exert a clamping force on the measurement plate, and thedeformations undergone by the plate in line with each roll locatedvertically in line with the gauges is measured by means of said gauges,in order to deduce therefrom the clamping force applied by the rolls inline with each gauge, and the actual clamping between rolls.

[0031] By using the strain gauges placed vertically in line with therolls, it is possible to measure the surface bending deformations of theplate that are caused by the rolls bearing on the plate, and to deducetherefrom, knowing the mechanical properties of the plate, the magnitudeof the bearing force on each gauge. From these measurements, it istherefore possible to have a precise knowledge of the characteristics ofthe leveler, from the standpoint of the geometry of the leveling pathdefined between the rolls.

[0032] Firstly, preferably, the plate has at least one row of gaugesthat is located so as to be placed vertically in line with one of therolls located near the entry of the leveler and at least one row ofgauges located so as to be placed vertically in line with one of theexit rolls. It is thus possible to determine the entry and exit clampingforces on the leveler and, for example, to consequently set the motorsfor controlling the position of the upper beam in a positioncorresponding to identical clamping at the entry and at the exit, inorder subsequently to be able to determine the difference in actualclamping between entry and exit, and therefore the difference inimbrication between the entry rolls and the exit rolls. It will be notedthat the gauges are not placed in line with the first, upper or lower,roll or in line with the last, upper or lower, roll so that themeasurements will be carried out only in line with rolls that are loadedjust substantially vertically.

[0033] Also preferably, a row of gauges includes at least one gaugelocated in the central line and a gauge on each side toward the edges ofthe leveler, thereby making it possible to determine, and thereforecorrect if necessary, differences in clamping between the sides of theleveler. In combination with the abovementioned measurements, it becomespossible to detect, and therefore also correct, dislocations of theleveler.

[0034] Also preferably, one row of gauges includes a central gauge andseveral lateral gauges placed so as to each be located vertically inline with each press roll of the leveler. It is therefore possible tofurther improve the precise knowledge of the characteristics of theleveler from the standpoint of the geometry of the leveling path definedbetween the rolls, in particular the transverse profile of this path,which is defined by the shape of the generatrix. of the rolls in contactwith the measurement plate.

[0035] It is then possible to act on the press rolls in order to correctdefects in parallelism between the rolls, for example by adjusting thepress rolls of the leveler so that the deformations measured by eachgauge for the same roll are equal and have predetermined values, in sucha way that the gap between two successive rolls, that is to say an upperroll and a lower roll, is constant over the width of the leveling path,or corresponds to predetermined values suitable for correcting thespecific defects of a sheet to be leveled.

[0036] What has just been described relates essentially tocharacteristics relating to the geometry of the leveling path, making itpossible to have the greatest possible knowledge about its geometry oncethe various elements of the leveler have been placed under conditionscorresponding to the working conditions, in particular under a loadcapable of overcoming the various amounts of play of the rolls and oftheir supports and of the adjustment and control members.

[0037] The invention thus makes it possible to assess the behavior ofthe leveler under load, by determining the overall clamping force invarious measured positions of the clamping control means and by deducingtherefrom a spring curve for the leveler, which can then be taken intoaccount for making the preadjustments for the work, according to thedimensional characteristics and mechanical properties of the strip to beleveled, and according to the magnitude of the imbrication of the rollsneeded to correct the known defects of said strip, for example. Insteadof considering the overall clamping force determined from all themeasurements carried out by all the gauges, more localized clampingvariations could also be determined, for example to distinguish thespecific spring of each column of the leveler, or to allow the behaviorof the press rolls during load variations to be independently monitored.

[0038] It should be noted that the instrumented plate according to theinvention is typically a steel plate having a high yield strength, forexample 1000 MPa, and a thickness for example of about 0.7 mm, and inany case a thickness very much greater than that of the strip to beleveled, which typically has a thickness of 0.1 to 0.2 mm for example.

[0039] To determine the characteristics of the plate, it is alsonecessary to take into account the following considerations:

[0040] the measurement plate must not undergo plastic deformation, whichcould in particular arise as a result of too deep an imbrication of therolls. Too deep an imbrication of the rolls may run the risk ofdeforming the measurement gauges excessively;

[0041] the thickness of the plate is determined so as to apply, byelastic bending, the leveling forces usually supported by the leveler;

[0042] furthermore, a maximum thickness of the plate is determined inorder to avoid having to reduce the sensitivity of the measurements; and

[0043] the yield strength of the plate is determined according to thethickness and so as to prevent plastic flow when the plate has to applythe usual maximum leveling forces.

[0044] In order for the measurements carried out to be reliable andreproducible, it is of the greatest importance for the measurementgauges to be precisely located in the position of greatest relativedeformation, that is to say at the top of the undulations generated byapplication of the clamping force. For this purpose, the positioningmeans include at least two sets of positioning gauges placed toward eachlateral edge of the plate respectively, as far away as possible fromeach other, vertically in line with the same roll, in order to allow theposition of the plate with respect to this roll in the levelingdirection, and therefore the relative position of all the rows ofmeasurement gauges with respect to their respective rolls to beaccurately determined.

[0045] For the position of the plate to be accurately adjusted, itincludes, on one edge transverse to the direction of leveling,adjustable bearing stops placed so as to bear against one of the endrolls, the entry roll or the exit roll, of the leveler at the height ofthe axis of said roll. By acting on these stops, which can be finelyadjusted for example by means of micrometer screws, the position of theplate is therefore adjusted so that the positioning gauges indicate thatthey are perfectly centered with respect to the roll. To facilitate thispositioning and increase its accuracy, the positioning gauges arepreferably gauges of a type known by the name “daisy chain”,conventionally made in the form of a set of five strain gauges joined inline over an overall length of around one centimeter. Each daisy chainis accurately cemented onto that face of the plate on the opposite sidefrom a work roll, so that the axis of the central gauge of the daisychain is in perfect vertical alignment with the axis of said roll.

[0046] The positioning of the plate is carried out by observing thesignals output by each gauge of the daisy chain, until symmetry isobtained with respect to the gauges located on each side of the centralgauge, on the one hand, and until a maximum is detected by the centralgauge, on the other hand, said maximum being indicative of the centralgauge being just in vertical alignment with the axis of the roll, inwhich the curvature of the plate is the most pronounced.

[0047] Other features and advantages of the invention will emerge fromthe following description of a device according to the invention and ofits operation.

[0048] Reference will now be made to the appended drawings in which:

[0049] FIGS. 1 to 5, which illustrate the principle and the constructionof a multi-roll leveler, have already been commented upon;

[0050]FIG. 6 is a partial view of a measurement plate according to theinvention;

[0051]FIG. 7 illustrates the positioning of the plate in the leveler, inaccordance with the invention;

[0052]FIG. 8 is a graph showing by way of an example a spring curvedetermined using the measurement plate; and

[0053]FIG. 9 is a graph illustrating the profile of the rolls under loadat the entry of the leveler, especially showing how the adjustment ofthe press rolls has an influence on the profile.

[0054] The instrumented plate 5 given by way of example and produced forone particular type of multi-roll leveler, shown in FIG. 6, is typicallya plate of sheet steel having a high yield strength, a thickness of 0.7mm and measuring 500 mm in the leveling direction and 1 m in thetransverse direction. It carries several rows of strain gauges 50cemented to the surface of the sheet, in the following manner:

[0055] A first row 51 of gauges is located on the upper face, to bepositioned vertically in line with the second lower roll 11 b, as may beseen in FIG. 7; a second row 52 of gauges is placed in a similar mannervertically in line with the penultimate lower roll; and a third row 53is preferably placed level with a central roll of the series of rolls.

[0056] Each of these rows has seven gauges, such as the gauges 51 a, 51b, 51 c, 51 f, 51 i, 51 j, 51 k, in the first row, placed vertically inline with the press rolls 22 a, 22 b, 22 c, 22 f, 22 i, 22 j, 22 k,respectively.

[0057] Other rows of gauges are placed on the lower face of the plate 5,such as a row of gauges 54 placed vertically in line with the secondupper roll 12 b, a row 55 placed vertically in line with the penultimateupper roll and a row 56 placed vertically in line with a central roll ofthe series of upper rolls. Each of these rows has for example threegauges, placed vertically in line with the press rolls 22 b, 22 f and 22j respectively. Additionally, placed in alignment on the row 54, andnear the edges of the plate, are positioning gauges 61, 62 consisting ofdaisy chains of five gauges aligned in the leveling direction, of a typeknown per se, and the central gauge of which is located precisely on theline 54.

[0058] The plate 5 also has two adjustable stops 60, each having a fixedpart 63 fastened to the plate 5 and a moving part 64 that can beadjusted with respect to the fixed part, for example by a micrometerscrew, and the end of which is positioned so as to butt against thefirst lower roll, as shown in FIG. 7.

[0059] To take a measurement, the plate 5 is placed between the lowerrolls and the upper rolls and clamping starts by actuating the motors 19a, 19 b. The indications given by the positioning gauges 61, 62 make itpossible to check that the row of gauges 54 is correctly positionedvertically in line with the roll 12 b and if necessary to correct itsposition using the adjustable stops 60, with a precision of the order of0.1 mm. This first step of the measurement is key for ensuring perfectparallelism between the rows of gauges and the rolls, and the precisepositioning of each alignment of gauges in the vertical plane passingthrough the axis of the corresponding roll.

[0060] The clamping measurements may then be made by means of thevarious gauges.

[0061] By varying the clamping, overall measurements, or measurementsintegrated over all or some of the gauges on the plate, will make itpossible, for example, to determine the forces supported by the beamsand the spring of the leveler. FIG. 8 shows by way of an example thespring curve for a column located on the exit side of a leveler,obtained by using the measurement plate according to the invention, thespring being plotted on the x-axis in mm and the roll clamping forcesplotted on the y-axis in daN.

[0062] Such a spring curve can then be incorporated into the leveleradjustment parameters.

[0063] By observing the values given by each of the gauges separately,it is possible to determine a load profile for each roll placed incorrespondence with a row of gauges. The graph in FIG. 9 shows, forexample, the profile of the entry rolls of a leveler. Plot 71corresponds to a 0 setting of the press rolls; plot 72 to a −0.05 mmsetting; plot 73 to a −0.1 mm setting. Each point on the plotscorresponds to a measurement gauge and the values indicated on they-axis represent the clamping of the rolls on the plate, this beingdetermined from the measurements taken. These measurements taken withthe instrumented plate according to the invention allow the usualadjustments to be validated, that is to say a setting of the press rollsof −0.1 mm, carried out empirically in order to obtain manifestly goodflatness. The measurements taken according to the invention thereforemake it possible to obtain a good image of the clamping forces along thetransverse direction that are actually applied in the leveler. They alsomake it possible to refine the adjustments of the press rolls in orderto obtain better flatness.

[0064] The invention is not limited to the embodiment of theinstrumented plate described above solely by way of example. Inparticular, the number and the arrangement of the rows of gauges and thenumber of gauges per row may be modified, according to the number ofrolls in the leveler, the number of press rolls and the measurementsthat are desired. In addition, the positioning gauges and the adjustablestops may be replaced with equivalent means suitable for positioning asprecisely as possible the rows of measurement gauges vertically in linewith the rolls.

[0065] It should also be noted that, although a priori it is envisagedto characterize the leveler for the maximum leveling width, using ameasurement plate of this width, it is also possible to characterize theleveler for working in a given sheet size, different from the maximumsize, using a measurement plate having dimensions identical to that ofthe product for which it is desired to characterize the leveler. Theplate will then preferably be placed so as to be centered longitudinallyin the leveler. The characterization of the leveler may then be usedsubsequently to adjust it, even for leveling sheet of smaller size.

1. A device for calibrating a multi-roll leveler in order to level ametal strip, comprising a set of lower rolls and a set of upper rolls,arranged approximately in a parallel manner, perpendicular to theleveling direction in which the strip to be leveled runs, characterizedin that it includes a measurement plate (5) made of metal, having a sizesuitable for being placed between the set of upper rolls and the set oflower rolls, extending approximately over the entire length of saidrolls, said plate having positioning means (61, 62; 63, 64) forpositioning it with respect to the rolls in the leveling direction, andstrain gauges (50) for measuring elastic deformations of the plate, saidstrain gauges being fastened to the plate so as to form severaltransverse rows (51 to 56) of gauges each located vertically in linewith one of said rolls, on the opposite face of the plate with respectto said roll.
 2. The device as claimed in claim 1, characterized in thatthe plate (5) has at least one row of gauges (51) located so as to beplaced vertically in line with one of the rolls located near the entryof the leveler and a row of gauges (52) located so as to be placedvertically in line with one of the rolls located toward the exit.
 3. Thedevice as claimed in claim 1, characterized in that one row of gaugeshas at least one gauge (51 f) located on the central line and a gauge(51 a, 51 b, 51 c, 51 i, 51 j, 51 k) on each side toward the edges ofthe leveler.
 4. The device as claimed in claim 3, characterized in thatone row of gauge has a central gauge (51 f) and several lateral gauges(51 a, 51 b, 51 c, 51 i, 51 j, 51 k) placed so as to each be locatedvertically in line with each press roll (22 a, 22 b, . . . 22 k) of theleveler.
 5. The device as claimed in claim 1, characterized in that thepositioning means comprise at least two sets (61, 62) of positioninggauges placed toward each lateral edge of the plate vertically in linewith the same roll, respectively, in order to allow the position of theplate with respect to this roll in the leveling direction to beaccurately determined.
 6. The device as claimed in claim 1 or 5,characterized in that the plate includes, on one edge transverse to thedirection of leveling, adjustable bearing stops (60) placed so as tobear against one of the end rolls, the entry roll or the exit roll, ofthe leveler level with the axis of said roll.
 7. A method forcalibrating a multi-roll leveler, using the device as claimed in any oneof the preceding claims, characterized in that the measurement plate (5)is placed in the leveler, positioned by the positioning means (60, 61,62) so that each row of gauge is located vertically in line with a roll,and the two sets of rolls are brought closer together by clampingcontrol means so as to exert a clamping force on the measurement plate,and the deformations undergone by the plate in line with each rolllocated vertically in line with the gauges is measured by means of saidgauges, in order to deduce therefrom the clamping force applied by therolls in line with each gauge.
 8. The method of calibrating a multi-rollleveler as claimed in claim 7, characterized in that the device asclaimed in claim 6 is used and the position of the plate (5) is adjustedby means of the adjustable stops (60) so that the positioning sensorsare located so as to be precisely in vertical alignment with the roll.9. The method of calibrating a multi-roll leveler as claimed in claim 7,characterized in that the overall clamping force in the various measuredpositions of the clamping control means is determined and a spring curvefor the leveler is deduced therefrom.
 10. The method of calibrating amulti-roll leveler as claimed in claim 7, characterized in that thepress rolls (22 a to 22 k) of the leveler are adjusted so that thedeformations measured by each gauge for the same roll are equal and havepredetermined values.